End-users of process oils are requesting increased solvency of these products as indicated by lower aniline point requirements. Simultaneously, the availability and supply of conventional naphthenic crude oil sources is declining. Thus, there exists a need in the art for a process that produces naphthenic base oils, particularly those base oils having a lower aniline point, from a lesser amount of naphthenic distillate.
U.S. Pat. Nos. 4,744,884, and 4,699,707, both to Moorehead, et al. disclose a process to produce lubricating oil fractions boiling above 650° F. (343.3° C.) having a pour point at or below 10° F. (−12.2° C.) and a viscosity index of at least 95. The process comprises hydrotreating a full-range shale oil and then hydrodewaxing the effluent from the hydrotreating step. The product from the hydrodewaxing step is passed to a hydrogenation reactor wherein it is contacted with a catalyst containing a hydrogenation metal component. After hydrogenating the product from the hydrogenation stage is fractionated into one or more lubricating oil fractions.
U.S. Pat. No. 5,976,354, Powers, et al. discloses a process whereby the practitioner can produce a diesel fraction, light oil fraction, and a finished oil. The process comprises the steps of mild hydrotreating, followed by catalytic dewaxing, and an optional aromatics saturation step after the catalytic dewaxing. The product from the catalytic dewaxing, or from the optional aromatics saturation step, is sent to a fractionation tower to separate the products. All of the above-cited references are hereby incorporated by reference.
There still exists a need in the art for a process that produces naphthenic base oils, particularly those base oils having a low aniline point, from a low quality feedstock.